The objective of this project is to further our knowledge concerning the role played by the basilar pontine nuclei mediating certain cerebro-cerebellar communications which certainly must represent an important component of voluntary motor performance. In this regard we propose to use combined Golgi-Electron Microscopic degeneration methods to investigate the inputs of corticopontine, cerebellopontine and tectopontine afferent systems to single, identified pontine projection and intrinsic neurons. In addition, the Golgi-EM procedure or intracellular injection of HRP will be used to investigate the presynaptic structures formed by the processes (axonal or dendritic) of intrinsic neurons and to confirm or deny the existence of recurrent collaterals arising from pontocerebellar axons. The second major avenue of investigation will examine the potential for axonal sprouting (plasticity) in the corticopontine and cerebellopontine systems. These studies will be carried out in both neonatal and adult animals by first combining a unilateral cortical lesion with a subsequent tritiated amino acid injection in the contralateral hemisphere. The resultant labeling pattern in the pons will then be studied for details of where sprouting has occurred. Subsequent EM studies of the synaptic organization under these conditions will involve a two-stage lesion process. The initial large, unilateral lesion will be followed some time later by a lesion in the contralateral hemisphere which will result in the degeneration of sprouted axons thereby marking their terminals for EM observation. If axonal sprouting and synapse formation can be documented, such studies will provide the necessary foundation for further experiments designed to test the efficacy of the newly formed synapses and perhaps to test agents suspected of promoted axonal sprouting and growth.